After having injected intramusculary the serum of patients of hypoplastic anemia into rats, the author made an attempt to study the adrenal cortical function of this disease, and obtained the following results. 1. After the first injection there was no change in electrolytic metabolism of serum, just about the same as in the case of ratio Na/K, and it increased in successive injections. 2. The weight of adrenal gland showed no change after the first injection, and was inclined to lose a little during succescive injections. 3. The total ascorbic acid of adrenals decreased after the first injection, while in succesive injections, it increased by degrees remarkably. After the cessation of successive injection it became normal. 4. After the first injection lipid granules in adrenal cortex became finer and decreased in number in zona fasciculata. While in succesive injections they became grosser and moved to inner side and after stopping successive injections they became finer again and many of regenerated granules appeared in sight. 5. With the progress of injections zona glomerulosa of adrenal cortex became hypertrophic, transitional zone became broader, and cells of zona fasciculata became slightly atrophic or degenerated. 6. As the results of these findings above mentioned, the idea, that the first injection produces stress (alarm reaction); and in the initial stage of successive injections, stress (stage of resistance) can be observed; but this stage of resistance disappearing gradually, there ensues the stage of repression of adrenal cortical function; and after the cessation of injections hyperfunotional stage reappears, seems to be reasonable. And these changes are definitely caused by anemia producing factor in serum of patients with hypoplastic anemia.